Chemokines are small, secreted peptides that control the migration of leukocytes along a chemical gradient of ligand, known as chemokine gradient, especially during immune reactions (Zlotnik et al., 2000, Immunity, 12:121-127). They are classified into four classes according to the location of the Cys residues at the N-terminus. The CXC class consists of chemokines with a pair of Cys separated by a single residue. The most prominent members of this class are interleukin-8 (IL-8, CXCL8), stromal derived factor-1 (SDF-I, CXCL12), gamma-interferon inducible protein-10 (IP-10, CXCLIO), platelet factor-4 (PF-4, CXCL4), neutrophil activating protein-2 (NAP-2, CXCL7) and melanoma growth stimulating activity (MGSA, CXCLI). The CC class of chemokines have two adjacent Cys at the N-terminus and include macrophage inflammatory protein-1 (MIP-Iα, CCL3; MIP-IjSa, CCL4), regulated upon activation of normal T expressed and secreted (RANTES, CCL5), monocyte chemoattractant protein-1 (MCP-I, CCL2). The CX3C class of chemokines contains two Cys separated by three residues at the N-terminus and are represented by fractalkine/neurotactin (CX3CL1). The C-class chemokines contain a single Cys at the N-terminus and are represented by lymphotactin/ATAC/SCM (CLI). Chemokine receptors are grouped according to their binding selectivity to chemokines. For example, CXCR4 binds SDF-I and CXCR5 binds B cell-attracting chemokine 1 (BCAI). The CXCR4 and SDF-1 interaction plays an important role in multiple phases of tumorigenesis, including tumor growth, invasion, angiogenesis, and metastasis.
CXCR4 is a seven transmembrane G protein coupled receptor (GPCR) (Herzog et al. DNA Cell Biol. 12: 465 (1993); Rimland et al. Mol. Pharmacol. 40: 869 (1991); WO03014153, WO02061087). Many medically significant biological processes are mediated by signal transduction pathways that involve G-proteins (Lefkowitz, Nature, 351:353-354, (1991)). G protein-coupled receptors (GPCRs) are integral membrane proteins containing 7 putative transmembrane domains (TMs). These proteins mediate signals to the interior of the cell via activation of heterotrimeric G proteins that in turn activate various effector proteins, ultimately resulting in a physiologic response.
CXCR4 plays a role in embryogenesis, homeostasis and inflammation. Moreover, CXCR4 has been shown to function as a coreceptor for T lymphotrophic HIV-I isolates (Feng, Y. et al. Science 272:872 (1996)). CXCR4 also plays a pleiotropic role in human cancer. Its expression is upregulated in many tumor types, including cancers of the breast, lung, colon, pancreas, brain, prostate, ovary, as well as hematopoietic cancers. Some literature reports suggest that SDF-1 may act through CXCR4 as a growth and/or survival factor for some tumors. CXCR4 is expressed on stem cell-like or tumor initiating subpopulations of many tumors, and may mediate the ability of these cells to support the recurrence and metastatic spread of cancers. Additionally, CXCR4 is expressed on endothelial precursor cells (EPCs), and its activity is required for incorporation of EPCs into functional vessels during angiogenesis. This may make a significant contribution to the vascularization and survival of tumors. CXCR4 signaling can also lead to induction of pro-angiogenic cytokines (e.g. VEGF), as well as integrins, adhesion molecules and matrix degrading enzymes that may mediate invasion by tumor cells. Furthermore, CXCR4 expression is detected on tumor infiltrating lymphocytes and fibroblasts, as well as tumor associated macrophages. These cells tend to suppress immune recognition and attack on the tumor, and remodel the tumor micro environment to encourage tumor growth and metastasis.
The multiple roles of CXCR4 in tumor growth, and metastasis, and its broad expression in many common tumor types, make this receptor an attractive target for therapeutic intervention using inhibitory agents. While peptide and small molecule inhibitors of CXCR4 and anti-CXCR antibodies have been identified or entered into the clinic, their utility has been limited by pharmacokinetic properties and toxicology. An agent, such as antibody or antibody-drug conjugate, that is selective, has a long half-life, improved efficacy and safety profile would be a desirable agent for use in the treatment of cancers.
Although there are various agents under development that target CXCR4, there exists a need for additional therapeutic agents targeting CXCR4 (such as antibodies or antibody-drug conjugates) that have improved efficacy and safety profile, and which are suitable for use with human patients. The antibodies and antibody-drug conjugates of the present invention are therapeutically useful anti-CXCR4 antibodies possessing a number of desirable properties such as reducing tumorigenesis, tumor growth, angiogenesis, and metastasis. Additionally, antibodies and antibody-drug conjugates of the present invention induce apoptosis of tumor cells.